Many proposals have been made and known for a solid catalyst component containing magnesium, titanium, an electron donor compound and halogen as essential components and a process for the polymerization or co-polymerization of olefins in the presence of a catalyst for polymerization of olefins comprising said solid catalyst component, an organic aluminum compound and an organic silicon compound. For example, JP-A-57-63310 and JP-A-57-63311 (The term "JP-A as used herein means an "unexamined published Japanese patent application") propose a process for polymerizing an olefin having 3 or more carbon atoms using a catalyst system comprising a solid catalyst component containing a magnesium compound, a titanium compound and an electron donor compound, an organic aluminum compound and an organic silicon compound having Si--O--C bond. However, these processes are not always satisfactory for obtaining highly stereoregular polymers in high yield, and further improvement has been demanded.
On the other hand, JP-A-63-3010 discloses a catalyst system for the polymerization of olefins and a process for polymerizing olefins using the same, the catalyst system comprising a solid catalyst component prepared by bringing a dialkoxymagnesium, a diester of an aromatic carboxylic acid, an aromatic hydrocarbon and a titanium halide into contact and subjecting the resulting product in a powdered state to a heat treatment, an organic aluminum compound and an organic silicon compound. JA-A-1-315406 discloses a catalyst system for polymerizing olefins comprising a solid catalyst component prepared by bringing titanium tetrachloride with a suspension formed by diethoxymagnesium with an alkylbenzene, adding phthalic dichloride thereto to react to obtain a solid product, and further contacting the resulting solid product with titanium tetrachloride in the presence of an alkylbenzene, an organic aluminum compound and an organic silicon compound, and a process for polymerizing olefins in the presence of said catalyst system. The foregoing known techniques focus on the development of a catalyst component having a high activity enough to allow the omission of a so-called deashing step, i.e., step of removing catalyst residues such as chlorine and titanium remaining in the polymer produced as well as on the enhancement of the yield of stereoregular polymer or an improvement in durability of the catalyst activity for polymerization, and achieved excellent results to these purposes.
The propylene polymer obtaining by using the forgoing catalysts, so-called a crystalline polypropylene, has a high rigidity and shows a superior heat-resistability caused by having generally a high heat-deforming temperature, a high melting point and a high crystallization temperature and is utilized in various uses, e.g., a container or a film other than a molded product of automobile or household appliances.
In recent years, however, from the standpoint of energy saving or conservation of resources related to the global environmental issue, it has been keenly desired to reduce the weight of plastics for use in automobile, household appliance, etc. In order to solve this problem, the thickness of molded plastic articles needs to be reduced while maintaining its strength such as impact strength. Regarding polyolefins, to improve of rigidity of resin has been an important problem by improving technology of compounding polymers and enhancing crystallinity of base polymer by polymerization technology, etc. in order to solve these problems.
However, the foregoing known techniques are not enough to solve the problems, and it is desired to develop a solid catalyst component for polymerizing olefins or a catalyst system using the same which can enhance the stereoregularity or crystallinity of base polymer itself.
The present invention is intended to solve the foregoing problems remaining in the prior art techniques. In other words, an object of the present invention is to provide a solid catalyst component and catalyst for polymerization of olefins, which can provide a superior stereoregularity polymer in high yield.